You'll get things thrown at you regardless of your intent or response. The anonymous violent protestors among the crowd don't likely know the cops personally, they're just there to inflict damage when they decide to throw something. You can choose to wear appropriate gear for what you're doing and prevent some damage, or eat a glass bottle to the face, arms, or legs (cops can do bike patrol AND riot control and use different gear -- there's no change in gear issuance needed). Wearing bike squad gear to a riot won't stop those assholes from doing harm. They might even prioritize you for a chance to see blood.